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BUSY BOLTERS Are you one?  The Shop Area
continues to pull in the most views on the Stovebolt. In August alone there were over 22,000 views in those 13 forums.
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Jul 21st, 2025 | | | | Joined: Feb 2006 Posts: 42 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2006 Posts: 42 | Does anyone know the original part number for a 1942 Chevy 235 engine piston? Also what does the wording SEMI mean on a box of old pistons on the box. Saw some Sealed Power pistons on the Ebay that had SEMI written on the box. | | | | | Joined: Feb 2006 Posts: 42 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2006 Posts: 42 | Sorry wrong ad They were TRW C-1047F -SeMI . Just having trouble getting standard size piston to replace the one I broke. | | | | | Joined: Jul 2002 Posts: 177 'Bolter | | 'Bolter Joined: Jul 2002 Posts: 177 | Chevy Part number 605474 is a Std. size 235 cast iron piston 1941-47 .
Semi is a over size piston that is in need of machining to what ever size is required. | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | "Semi" means "semi-finished". Those pistons had to have the final diameter machined by the purchaser. Now, here's the problem with that- - - -since a lot of pistons aren't round, semi finished pistons have to be finished on a cam-grinding machine. The widest point of the piston skirt is a narrow area at right angles to the wrist pin, and there's a strut made of a piece of material called "Invar" that has a very low expansion rate when heated. The piston gets round as it comes up to normal operating temperature.
Cast iron stovebolt pistons that I've measured are almost round, so apparently those were not cam ground. If you're looking for a cast iron piston, send me a PM. I've got a bunch of good-condition used ones, just need to know what size you need.
Edit:
I just re-read your post- - - -you need a standard size piston. Do your pistons have flat tops or are they domed? Cast iron 235 flat top pistons can be replaced with light weight aluminum ones, which also result in longer life for the Babbit connecting rods and quicker acceleration. There are plenty of 1954-62 standard size aluminum pistons available. Cast iron oversize pistons can also be ground down to standard diameter by any competent machinist who has a lathe and a tool post grinder.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Feb 2006 Posts: 42 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2006 Posts: 42 | Found some pistons yeah!!!! | | |
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